Centrifugal casting mold

ABSTRACT

A centrifugal casting mold comprises inner and outer coaxial steel shells with an interposed intermediate packing layer of granular material. An insert such as a helical band may be provided in the packing layer. The inner shell is deposit welded on the inner surface of the packing layer and optionally the outer shell may also be formed by deposit welding on the outer surface of the packing layer.

United States Patent Oehler et al.

[ Nov. 13, 1973 CENTRIFUGAL CASTING MOLD Inventors: Hans Hermann Oehler, Wattenscheid-Hontrop; Johannes Jansen, Bochum, both of Germany Assignee: Fried. Krupp Huttenwerke AG Filed: June 28, 1971 Appl. No.: 157,430

US. Cl 249/135, 164/286, 249/137 Int. Cl B22d 13/02 Field of Search 164/286, 298, 114;

References Cited UNITED STATES PATENTS 10/1923 Anthony 164/114 X 1,555,578 9/1925 Howe 29/4745 X 1,678,929 7/1928 Yeomans 164/298 X 1,942,304 l/l934 Mylting 29/474.l X

1,573,089 2/1926 Rice 164/291 Primary Examiner-Robert D. Baldwin Attorney-Eric H. Waters et a1.

[57] ABSTRACT 6 Claims, 4 Drawing Figures PATENXED RM 1 3 1973 Fig 3 1 CENTRIFUGAL CASTING MOLD BACKGROUND OF THE INVENTION a. Field Of The Invention The invention relates to a centrifugal casting mold with a coaxial arrangement of three elements inclusive of an outer tubular shell and an inner tubular shell, and also to a methodof producing the mold.

b. Prior Art Centrifugal casting molds are used for manufacturing cast tubes. They rotate in casting machines with simultaneous external cooling with water or the like, and they may have, for instance, the following dimensions:

diameter: 100 to 1,000 mm length: up to 800 mm Conventional centrifugal casting molds are produced, in general, by forging; and they are subsequently cut withmultiple-point chip removal so as to achieve high accuracy. As a result of these necessary operations, the production costs are correspondingly high, and, consequently, the'fin'al'product is proportionally expensive.

The capability of the material to withstand high temperatures and numerous temperature changes over long periods of time and without formation of cracks or fissures is essential for high output production of tubes and also for the durability of the centrifugal casting mold itself. 7

It is evident that the required properties can be obtained from the materialitself only to a limited extent, as it depends upon the development, and reduction of plastic deformation, respectively from the stresses caused by the same, if the formation of the cracks or fissures in the course of multiple temperature changes, respectively frequent stress reversals, can be influenced.

During the past years, only certain materials have been discovered and systematically examined in regard to their service load with the result that a certain output cannot be exceeded in case that stress accumulations in the inner wall of the mold, resulting from the plastic deformations, exceed the elastic limit, or the tensioncompression ,fatigue strength. The, development of harmful self-contained stresses and their influence on the durability of the machine parts stressed in this manner is already sufficiently scientifically clarified and The possibility of increasing the output of centrifugal casting molds by changing the analytic properties or the heat treatment is limited. The prospect of influencing the output in broader limits can be achieved onlyv be redesigning the construction of the centrifugal casting mold and its treatment in the factory during the operation. In the search for achieving these objectives, attempts have been made to. treat the inner surface of the centrifugal casting mold with the intention to develop a finely distributednetworkof temperature fissures or,

cracks in the early stages of operation, and thusly to obtain a breathing. surface of the inner wall of the mold, which responds more readilyto the temperature change operations and subsequent stresses, and stress reversals. German Patent No. 972,528 shows such measures for enhancing the durability of the chemically uniform material.

I Further improvements have been achieved by utilization of centrifugal casting molds.in which the inner shell is subdivided'by grooves and then closed again by 934,967). This has indeed resulted in increased durability and economic effects, but such constructions were also limited, in particular if faster operation sequence was desired.

SUMMARY OF THE INVENTION It is an object of the invention to provide a centrifugal casting mold with increased effectivity and durability and also to provide a method for production of such centrifugal casting mold.

According to the invention, the centrifugal casting mold comprises first, second and third annular, coaxial elements metallically interconnected, the first element being an inner tubular shell, the third element being an outer tubular shel1,'and said second element being a packing tube interposed between the inner and outer shells. The packing tube is constituted of granular material and said inner tubular shell is a layer of weld material deposited on said packing tube.

These three elements are constituted of metallic materials with different properties, and in particular, steel having such different properties.

The invention further contemplates a method of manufacturing a centrifugal casting mold comprising the' steps of supporting a tubular layer of the granular material in the desired .thickness, partially melting the granular material to coalesce the material into a selfsustaining tube deposit welding the material of the inner shell onto the innersurface of said tube, and then attaching the outer shell to the outer surface of the said tube.

DESCRIPTION OF THE DRAWING FIG. ,1 is a side elevation view,partially broken away and in section, of a centrifugal casting mold according to the invention,

' FIG. 2 is a sectional view takenalong line A'A in FIG. 1,

. FIG. 3 is a side elevational view similar toFlG. l of another embodiment of -casting mold; according to the invention, and

FIG; 4 is a sectional view taken on line 13-3 in FIG.

. DETAILED DESCRIPTION Referring to the drawing, t herein are shown centrifugal casting molds respectively comprising an outer, tu-

bular shell 1, an inner, tubular shell 2 and an intermediate packing element of granular material interposed between the innerand outer shells, The shells 1 2 are interconnected to the packing element, as will be explainedfmofe fully hereafter, and are coaxial therewith.

. The following technologicalproperties are provided for the individual elements or layers: For the inner tubular shell 2: high temperature change resistance strength high heat conductivity For the outer tubular shell 1: medium strength high deformation capability The individual elements are constituted of steel and in the following the composition of the steels is given for the different layers:

The inner tubular shell 2 The rest being iron with the usual contaminations (P and S) The packing element The rest being iron with the usual contaminations (P and S) The outer tubular shell 2 The rest being iron with the usual contaminations (P and S) v The packing element can be made exclusively of granulated material as shown in FIG. 1.

However, it can also be advantageous to incorporate a skeletal insert in the packing element constituted of round or flat bars or rods. The insert may be in the form of a helical band 3 as shown in FIG. 2 and the band is preferably made of the same material as the granules. The skeletal insert may also have other forms such as mats, plaitings etc.

It is advantageous if the thickness of the inner tubular shell 2 is 3 to 10 mm, that of the packing tube is 5 to 15mm and that of the outer tubular shell 1 is 15 to 40 Preferably, the thickness of the inner tubular shell is 5 to 8 mm, the packing tube 10 to 12 mm and the outer tubular shell 15 to 25 mm.

In the process of manufacturing the centrifugal casting mold, according to the invention, the outer tubular shell may be produced first and then the material needed for the formation of the packing tube, i.e. the granular material and, optionally, the round or flat bars or rods or the helical band, are introduced into the outer tubular shell, the intermediate spaces in the insert (bars, rods or band) being filled by the granular material. Advantageously, the granular material is partially melted when it is used alone and when it serves as filling of the intermediate spaces as well. Subsequently, the inner tubular shell is secured to the packing tube, preferably by deposit welding of the particular material, i.e. the aforementioned steel of the inner tubular shell.

In order to produce a packing tube consisting solely of granular material, the granular material is preferably filled in an auxiliary tube, is passed under a scraper in order to establish the thickness of the layer and finally, is partially melted by the action of a welding head to coalesce the material and form a self-sustaining tube. If the inner tubular shell is produced first, the material of the outer tubular shell can be deposit welded on the packing tube so as to form the outer tubular shell.

The particular advantages of the construction according to the invention are to be seen in the uniform cooling effect throughout the centrifugal casting mold and in the prolonged durability.

What is claimed is:

1. A centrifugal casting mold comprising first, second and third annular, coaxial elements secured together as a compound metallic tube, the first element being an inner tubular shell, the third element being an outer tubular shell, and said second element being a packing tube interposed between the inner and outer shells and being constituted of metallic granular material, the granules of which have been partially melted to coalesce, at least one of said tubular shells being a layer built up of metallic weld material deposit welded onto the surface of said packing tube.

2. A mold as claimed in claim 1 wherein said packing tube includes a skeletal insert.

3. A mold as claimed in claim 2 wherein said skeletal insert comprises bars.

4. A mold as claimed in claim 3 wherein said bars are arranged in the form of a helical band.

5. A mold as claimed in claim 1 wherein said inner shell is a steel with high resistance to temperature change, low expansion capacity and high strength, said packing tube being a steel with high toughness and low strength, and high heat conductivity, said outer shell being a steel with medium strength and high deformation capability.

6. A mold as claimed in claim 5 wherein the steel of the inner tubular shell has the following composition: 0.08 '0.80 C; 0.15 -3.0 Si; 0.20 2.0 Mn; 0.30 --25.0 Cr; 0.20 --3.0 Mo; 0.30 0 15.0 Ni;

0.10 --O.70 V; 0.10 -1.5 W; and the rest iron, the

steel of the packing tube having the following compositum:- 1

0.05 -0.25 C; 0.10 l.0 Si; 0.10 1.0 Mn, and the rest iron, andthe seel of the outer tubular shell having the following composition:

0.20 --0.50 C; 0.15 -0.80 Si; 0.20 1.0 Mn; 0.30 -2.0 Cr; 0.15 1.5 Mo; 0.20 2.5 Ni;

and the rest iron. p 

1. A centrifugal casting mold comprising first, second and third annular, coaxial elements secured together as a compound metallic tube, the first element being an inner tubular shell, the third element being an outer tubular shell, and said second element being a packing tube interposed between the inner and outer shells and being constituted of metallic granular material, the granules of which have been partially melted to coalesce, at least one of said tubular shells being a layer built up of metallic weld material deposit welded onto the surface of said packing tube.
 2. A mold as claimed in claim 1 wherein said packing tube includes a skeletal insert.
 3. A mold as claimed in claim 2 wherein said skeletal insert comprises bars.
 4. A mold as claimed in claim 3 wherein said bars are arranged in the form of a helical band.
 5. A mold as claimed in claim 1 wherein said inner shell is a steel with high resistance to temperature change, low expansion capacity and high strength, said packing tube being a steel with high toughness and low strength, and high heat conductivity, said outer shell being a steel with medium strength and high deformation capability.
 6. A mold as claimed in claim 5 wherein the steel of the inner tubular shell has the following composition: 0.08 -0.80 % C; 0.15 -3.0 % Si; 0.20 -2.0 % Mn; 0.30 -25.0 % Cr; 0.20 -3.0 % Mo; 0.30 0 15.0 % Ni; 0.10 -0.70 % V; 0.10 -1.5 % W; and the rest iron, the steel of the packing tube having the following composition: 0.05 -0.25 % C; 0.10 -1.0 % Si; 0.10 -1.0 % Mn, and the rest iron, and the seel of the outer tubular shell having the following composition: 0.20 -0.50 % C; 0.15 -0.80 % Si; 0.20 -1.0 % Mn; 0.30 -2.0 % Cr; 0.15 -1.5 % Mo; 0.20 -2.5 % Ni; and the rest iron. 